Method for handling a stator bar using a pit

ABSTRACT

A method for handling a stator bar at a stator bar facility having a stator bar workstation, an in-ground pit proximate to and at an elevation below the workstation and a stator bar transport proximate to the in-ground pit including: loading the stator bar onto the stator bar transport; turning the stator bar at least 45 degrees in a vertical plane; positioning at least a third of a length of the stator bar down into the in-ground pit, aligning a first end of the bar with the workstation, and turning the bar to reverse positions of the ends of the bar, such that a second end of the bar is aligned with the workstation.

RELATED APPLICATIONS

This application is a divisional of application Ser. No. 11/159,334 (nowU.S. Pat. No. 7,735,211), filed Jun. 23, 2005 and claims the benefit ofU.S. Provisional Application Ser. No. 60/628,931, filed Nov. 19, 2004,which applications are incorporated in their entirety by referenceherein.

BACKGROUND OF THE INVENTION

The present invention relates to large stator bars that are used inpower and industrial generators, handling these bars before they areinstalled in a stator, and fitting header clips to the bars duringassembly.

Stator bars are typically large, long and heavy, e.g., 35 feet long andhundreds of pounds (lbs.). The bars are generally straight and extendthe length of a stator. When seated in a stator, the straight sectionsof the stator bars form a cylindrical array around a rotor. The ends ofthe stator bars extend axially from opposite ends of the stator. The endportion of the stator bars extend from the ends of the stator and arecurved to form end turns. The ends of stator bars are connected throughcopper or stainless steel fittings and water-cooled connections to formcontinuous hydraulic winding circuits.

The ends of the bars are each connected to a hydraulic header clip. Thehydraulic header clip serves as an electrical and a cooling flowconnection for the armature winding bar. The hydraulic header clip is ahollow connector that includes an enclosed chamber for ingress or egressof a cooling liquid, typically deionized water. At one open end, theclip encloses the ends of the copper strands of the armature windingbar.

A braze alloy bonds the end sections of the strands to each other and tothe hydraulic header clip. A hydraulic header clip fitted to the end ofthe stator bar is brazed to the bar. The bar is preferably heldvertically during the braze operation.

To hold the bar vertically there is a need for a braze station that canaccommodate a long stator bar in a vertical position. There is also aneed for supports that can position a stator bar vertically in a brazestation and rotate the stator bar from a horizontal position to avertical position. In the past, stator bars have been positionedvertically while the clip is brazed. Buildings with very high roofs andbrazing workstations elevated above the vertical end of a stator barhave been required for brazing vertical stator bars. These high roofbuildings and elevated workstations are expensive to construct. There islong-felt need for facilities for brazing stator bars that areadvantageous, e.g., less expensive to construct, then prior facilities.

BRIEF DESCRIPTION OF THE INVENTION

A stator bar facility is disclosed including: a stator bar workstation;an in-ground pit below the workstation; a stator bar elevator extendingfrom the workstation pit, and a coupling mechanism attached to theelevator, wherein the coupling mechanism further comprises a rotationalmount to receive at least one stator bar, wherein the rotational mountenables the received stator bar to be turned from a substantiallyhorizontal position to a substantially vertical position.

In another embodiment, the stator bar brazing facility includes: anin-ground pit below the workstation; an elevated bridge spanning thein-ground pit; a stator bar braze station and coupled to the bridge; astator bar elevator extending from the workstation pit, wherein saidelevator further comprises an extendible arm, and a coupling mechanismattached to the arm of the elevator, wherein the coupling mechanismfurther comprises a rotational mount to receive at least one stator barand is adapted to rotate the stator bar in a substantially verticalplane.

A method for handling a stator bar at a braze station is also disclosed,where method comprises: lifting the stator bar from a platform, whereinthe stator bar is in a substantially horizontal orientation on theplatform; rotating the stator bar from the horizontal orientation to asubstantially vertical orientation; positioning a upper end of the barin alignment with a brazing station and a lower end of the bar in a pit;rotating the bar to reverse positions of the ends of the bar; andreturning the stator bar to a horizontal orientation.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of a liquid-cooled stator windingarrangement illustrating the stator, stator bars and hydraulic headerclips coupled to inlet and outlet coolant headers.

FIG. 2 is a perspective view of the end of an armature winding barshowing the tiered rows of hollow and solid strands, and interleavingsheets of braze material.

FIG. 3 is a perspective exploded view of the end of an armature windingbar inserted into a hydraulic header clip, with braze material and aclip cover shown to the side of the clip.

FIGS. 4, 5 and 6 are side, end and top views, respectively of a brazestation for attaching end clips to winding bars. Line 4-4 in FIG. 6indicates the view shown in FIG. 4. Line 5-5 in FIG. 6 indicates theview shown in FIG. 5.

FIG. 7 is a top view of a braze station illustrating the loading ofstator bars on the stator bar transport in the workstation pit.

FIG. 8 is a side view of the braze station showing the stator bartransport extended to receive a stator bar from a loading station.

FIG. 9 is a top view of the braze station showing the transport movingthe stator bar over the pit.

FIG. 10 is an end view of a braze station showing the stator bar turnedto vertical position and being moved into position for brazing.

FIG. 11 is an end perspective view of a cradle for holding stator barsin the braze station.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 illustrates a liquid-cooled stator bar arrangement for a statorin a typical liquid-cooled generator. A stator core 10 has stator coreflanges 12 and core ribs 14. Stator bars 16 (also referred to asarmature winding bars) pass through radially extending slots in thestator core and are capped at opposite ends by hydraulic header clips 18fitted to the ends of the bars. Inlet hoses 22 connect an inlet clip 18to an inlet coolant header 24. Outlet hoses 26 connect an outlet clip 18to an outlet coolant header 28. Each stator bar forms a half an armaturecoil. A pair of stator bars linked at their opposite ends form acomplete armature coil. Copper or stainless steel fittings 20 connectadjacent ends of the stator bar pairs to form the complete armaturecoil.

FIG. 2 is a perspective end view of an stator bar 16 without a hydraulicheader clip. The bar is a rectangular array of solid 34 and hollow 36copper strands. FIG. 3 is a perspective view of the end of an armaturewinding bar 16 inserted in a clip 18 with braze strips 30 and a brazesheet 50. A clip cover 32 is shown to the side of the clip 18. In FIG.2, the braze strips 30 are interleaved between tiered rows of solid thecopper strands 34 and rows of hollow strands 36 of the bar 16. Justprior to brazing and at the end of the stator bar, braze strips areinserted between the strands 34, 36. In addition, the braze sheets 50and clip 32 are assembled in the clip 18.

The hydraulic header clip 18 (also referred to as a stator bar clip) isformed of an electrically conductive material, such as copper. The clip18 is hollow and includes a rectangular collar 38 that slides over theouter side surfaces of the end of the armature winding bar 16. Arectangular slot 39 in the collar receives the end of the armaturewinding bar and interleaved strips 30 of the braze alloy. The clip cover32 fits into the matching rectangular slot 39 in the side of the collar38. At the other end of the clip 18 is a cylindrical coupling end 40that is configured to connect to the coolant circuit.

The pre-braze positioned braze alloy strips extend beyond the ends ofthe short solid strands. The height of the alloy pre-positioned beforebrazing is selected so that the braze alloy will entirely melt duringthe braze process and not flow into the open ends of the extended hollowstrands.

During brazing, the stator bar is held in a vertical position and theend of the bar is horizontal. Melted braze alloy forms a pool over thesolid strand ends of the stator bar. After brazing, the braze alloyforms a braze alloy isolation coating over the end of the armature bar(but not the end of the hollow strands). The isolation layer shields thesolid strand ends and the joints from the coolant passage in the clip.The braze alloy also bonds the clip to the strands and the strand endsto each other.

FIGS. 4, 5 and 6 are side, end and top views, respectively, of a brazestation 90 for vertically brazing stator bars. The braze station 90includes a pit 91, a bridge 92 over the pit and a stator bar elevator 94extending form the bottom of the pit 91 to the bridge. The in-ground pit91 provides a large volume within which to reposition stator bars, e.g.,to rotate the bar in a vertical plane while the center of the bar is atthe level of the bridge 92. The in-ground pit may have a depth of twelve(12) feet, a length of forty (40) feet and a width of thirty-two (32)feet (which is about the length of a stator bar). The dimensionsdisclosed herein are exemplary and a braze station may be designed withdifferent dimension for a particular application of stator bars. Thedimensions of the in-ground pit may be sufficient to allow a stator barto be rotated about its center, where the bar center is at the elevationof the bridge and is generally aligned with the mid-point of the bridgelength.

Within the in-ground pit 91 is a deep pit 96 that is vertically alignedgenerally with the braze workstation 95 and the mid-point of the bridge92. The deep pit 96 may be cylindrical. The deep pit allows the statorbars to be lowered vertically until the upper end of the bar is levelwith the workstation. For example, the deep pit 96 may have a bottomthat is below the bridge a distance equal to the length of a stator bare.g., thirty-one and one-half feet, and the depth below ground level oftwenty-three and one-half feet. The expense of excavation of thein-ground pit 91 and deep pit 96 is minimized by limiting the horizontalcross section of the deep pit 96 to an area sufficient to raise andlower a vertical stator bar and limiting the in-ground pit 91 to a depthsufficient to allow the stator bar to rotate about the upper limit ofthe distance traversed by the elevator 94.

The vertical braze station 90 may be in a factory bay with a roof thathas sufficient less clearance, e.g., twenty-five feet, for handling ofstator bars, such as to allow for a crane ceiling height. The bridge 92in the station may be elevated to reduce the needed excavation depths ofthe pits 91, 96. The bridge 92 has workstations 95 to allow techniciansto braze the ends of the stator bars which are held vertically withinthe pit. Associated with the bridge are brazing hoods and otherequipment (not shown) needed to braze the hydraulic clips to the end ofthe stator bars. The stator bars are stored horizontally on storageplatforms 98 on either or both sides of the pit 91. The platforms aresubstantially horizontal, but may be on a slight incline such as up to10 degrees from horizontal. The bars may be mounted on cradles 110 (FIG.13) at the platforms.

An elevator 94 in the pit and adjacent the bridge holds the stator barswhile they are in the pit. Instead of an elevator, a crane or otherstator bar handling mechanism may be used to move the stator bar from aplatform 98 to the pit, and to rotate the bar so that it may be alignedwith a workstation. The stator bars are supported by a cradle 110 thatis latched to the elevator 94. One cradle may hold a pair of statorbars. The elevator 94 moves the stator bars with respect to theworkstations 95 and storage platforms 98. The elevator moves the statorbars and cradle between the storage platforms 98 and the workstations,and turns the stator bars between horizontal and vertical positions. Theelevator may comprise a pair of vertical rails 99 in a frame that ismounted over the deep pit 96 and sits on the floor of the shallower pit91. An electric motor 101 drives the elevator 94 up and down the rails99 and thereby raises and lowers the cradle 110 and stator bars. Inaddition, the motor 101 may rotate the cradle in a vertical plane.

FIG. 7 is a schematic top view showing the loading of a stator bar 100and cradle 110 from the loading platform 98 to the elevator 94. A dashline through the bridge shows the elevator 94 underneath the bridge. Aworkman 102 stands at the workstation 95 that moves up and down. Asshown in FIG. 7, the workman 102 may be at the same level as are otherwork persons 103 on the bridge. In contrast, FIG. 10 shows that theworkstation 95 may move vertically to better position the workman andthe braze hood 106 with respect to the end of the stator bar.

As shown in FIG. 8, the elevator 94 extends its arm 104, e.g.,telescoping arm, outward to grasp a cradle 110 with one or more statorbars from the loading platform 98. The arm has on a distal end acoupling and latching mechanism 105, which may be a pair of fingers thatgrasp a connection on a cradle holding the stator bars. The latchingmechanism further comprises a rotational attachment that enables thestator bar and its cradle to be rotated in a vertical plane about thedistal end of the elevator arm 104.

The stator bars 100 are in a horizontal position as they are moved fromthe storage platform 98 to the pit 91. The elevator 94 raises the cradleand its stator bars and turns the cradle and bars to a verticalorientation. Raising the stator bars allows the cradle and stator barsto be lifted off the platform. The vertical stator bars are lowered sothat their upper ends are within reach of the workstation 95. Theworkstation 95 may be raised or lowered and moved to the left or right(parallel to the bridge) to be properly positioned with respect to thestator bar ends. In addition, the elevator arm 104 may retract or extendthe bars 100 (in a direction perpendicular to the bridge) to assist inpositioning the bars with respect to the workstation. The braze stationmay provide six degrees of motion to position the ends of the statorbars in the braze hood. The six degrees are: up-down of bars andworkstation, forward-back of bars, left-right of workstation.

The workstation may include a braze housing 106 that is used to heat andbraze the end of the stator bar to the clip. At the workstation 95, theupper ends of the stator bars are mounted in the brazing hood 106 wherethe clip is brazed to the stator bar. The workstation 95 may be raisedor lowered (compare FIGS. 8 and 10) to orient the workstation to thebest position with respect to the end of the stator bar. Once the clipshave been brazed to the stator bars, the elevator arm 104 extents thestator bars and rotates them 180° (see circular arcs in FIG. 4) to bringthe opposite ends of the stator bars up to the workstation 95, as isshown in FIGS. 9 and 10. When both ends of the stator bars have beenbrazed with hydraulic clips, the elevator 94 turns the stator bars to ahorizontal position and the arm 104 extends to move the stator bars andcradle back to the loading platform 98.

FIG. 11 is a perspective end view of a stator bar cradle 110 and withtwo stator bars 100 mounted thereon. The cradle 110 is a rectangularframe having longitudinal beams and crossbeams that provide a rigidsupport for the stator bars. The stator bars may be loaded on the cradleat the platform 98 adjacent the braze station 90.

A stator bar holding cradle 110 secures a stator bar as the hydraulicheader end clips are attached to the bar. The cradle is a protectivedevice to avoid direct handling of the bars and avoid damage to thebars. In addition, the cradle serves as an interface to the elevator 94to ensure an engagement for multi-positional handling by the elevator.The stator bar holding cradle 110 provides multi-positional handling ofthe stator bar. The cradle has at least three and preferably six degreesof freedom restraints on the bar for vertical position operation.

The restraint system for the cradle 110 comprises angle adjustable twoside-clamping grippers 112 arranged in an array along the length of thecradle. There may be for example six stator bar grippers 112 spacedevenly along the length of the cradle to grasp the straight section of astator bar. These grippers are arranged lengthwise along the stator barsled and are pivotably attached to the sled. The pivoting movementallows the grippers to adjust for slight bowing and other variations inthe stator bar. The clamp grippers 112 grasp the straight section of astator bar 100. At each end turn section of the bar are two adjustablearms with end-turn clamp grippers 114 to grasp the end turns. The endadjustable grippers 114 have hydraulic expandable arms 116 that areadjusted to fit different bar arm lengths. The cradle 110 has a90-degree (perpendicular) dual pin coupling system 118 to securelyengage with a cradle connector, e.g., a pair of fingers, on the elevator94.

The dual pin handling engagement and locking mechanism 188 may be at thecenter of the cradle. The dual pin mechanism may be a bracket of a pairof rectangular tubes that receive fingers from the elevator. The fingersengage the rectangular tubs and are locked to the tubes so that thecradle is securely attached to the elevator 94.

While the invention has been described in connection with what ispresently considered to be the most practical and preferred embodiment,it is to be understood that the invention is not to be limited to thedisclosed embodiment, but on the contrary, is intended to cover variousmodifications and equivalent arrangements included within the spirit andscope of the appended claims.

1. A method for handling a stator bar at a stator bar facility having astator bar workstation, an in-ground pit proximate to and at anelevation below the workstation, and a stator bar transport proximate tothe in-ground pit, wherein the method comprises: loading the stator baronto the stator bar transport; turning the stator bar at least 45degrees in a vertical plane; positioning at least a third of a length ofthe stator bar down into the in-ground pit; aligning a first end of thebar with the workstation, and turning the bar to reverse positions ofthe ends of the bar, such that a second end of the bar is aligned withthe workstation.
 2. The method of claim 1 further comprising loweringthe stator bar into the pit in conjunction with turning the stator bar,wherein the stator bar is lowered by the stator bar transport.
 3. Themethod of claim 1 wherein the stator bar is turned from a substantiallyhorizontal position to a substantially vertical position.
 4. The methodof claim 1 wherein the workstation is elevated above ground level and atleast one-half of a length of the stator bar is within the pit when thestator bar is turned to a vertical position.